Show HN: DuckDB community extension for prefiltered HNSW using ACORN-1

A fork of duckdb-vss that integrates the ACORN-1 algorithm to push filter predicates into HNSW graph traversal, solving the upstream limitation where WHERE clauses applied post-index often return fewer results than requested. It uses selectivity-based strategy switching (post-filter above 60%, ACORN-1 for 1-60%, brute-force below 1%) and requires no special syntax, as the optimizer automatically detects eligible query patterns.